1. Field of the Invention
The present invention relates to an image display apparatus having a spacer.
2. Description of the Related Background Art
Among the prior image display apparatus, there are known ones including a support member, called a spacer, in an air-tight container including an image display member, such as a liquid crystal display apparatus, a plasma display apparatus, an electroluminescence apparatus, and an electron beam display apparatus.
In the following, there will be explained an electron beam display apparatus as an example of the image display apparatus having the aforementioned spacer.
FIG. 20 is a perspective view showing an example of a display panel of a plate image display apparatus utilizing an electron emitting element of a cold cathode type, in which a part of the panel is cut off in order to show the internal structure. A rear plate 3115, a lateral wall 3116 and a face plate 3117 constitute an outer envelope (air-tight container) for maintaining the interior of the display panel in a vacuum state.
On the rear plate 3115, there is fixed a substrate 3111, on which N×M cold cathode elements 3112 are formed in a matrix shape (N, M being integers equal to or larger than 2 and suitably selected according to a desired number of display pixels). The N×M cold cathode elements 3112 are also wired by row wirings 3113 of a number M and column wirings 3114 of a number N. A part constituted by these substrate 3111, electron emission elements 3112 of cold cathode type, row wirings 3113 and column wirings 3114 is called a multi electron beam source. Also, in at least crossing portions between the row wirings 3113 and the column wirings 3114, an insulating layer (not shown) is provided between both wirings to achieve electrical insulation.
On a lower surface of the face plate 3117, there is formed a fluorescent film 3118 of a phosphor, which is divided into phosphors (not shown) of three primary colors of red (R), green (G) and blue (B). A black colored member (not shown) is provided between the phosphors of respective colors constituting the phosphor film 3118, and a metal back layer 3119 composed for example of Al is provided on a surface of the phosphor film 3118 at the side of the rear plate 3115.
Electrical connecting terminals Dx1–DxM and Dy1–DyN are provided for electrically connecting the display panel and an unrepresented electrical circuit. The terminals Dx1–DxM are electrically connected with the row wirings 3113 of the multi electron beam source, while the terminals Dy1–DyN are electrically connected with the column wirings 3114 of the multi electron beam source, and a terminal Hv is connected with the metal back 3119.
The interior of the air-tight container is maintained at a vacuum of about 1.3×10−3 Pa, and, with an increase in the display area of the image display apparatus, there is required means for preventing a deformation or a destruction of the rear plate 3115 and the face plate 3117 by a pressure difference between the interior of the air-tight container and the exterior thereof. In FIG. 20, there is provided a spacer 3120 constituted of a relatively thin glass plate, for withstanding the atmospheric pressure. In this manner the substrate bearing the multi beam electron source and the face plate 3116 bearing the phosphor film 3118 are maintained at a gap less than a millimeter to several millimeters whereby the interior of the air-right container is thus maintained at a high vacuum.
In an image display apparatus employing the display panel explained above, when a voltage is applied to the cold cathode element 3112 through the external terminals Dx1–DxM and Dy1–DyN, electrons are emitted from each cold cathode element 3112. At the same time, a high voltage of several hundred volts to several killovolts is applied to the metal back 3119 through the external terminal Hv to accelerate the emitted electrons thereby causing a collision with an internal surface of the face plate 3117. Thus the phosphor of each color constituting the phosphor film 3118 is excited to emit light, whereby an image is displayed.
The spacer 3120 is positioned efficiently in a number required structurally. In case the spacer 3120 is made shorter than the image area and is positioned within the image area, it is fixed by a connecting member within the image area of the rear plate 3115 and/or the face plate 3117.
Also as disclosed in Japanese Patent Application Laid-open Nos. 9-179508 and 2000-251796, a spacer 3120 longer than the image area can attain a structure resistant to the atmospheric pressure by fixing both ends only. In such case, there may be assumed a method of fixing support members in advance to both ends of the spacer 3120 and fixing such support members with the rear plate 3115 or the face plate 3117 by means of adhesion members.
In an image display apparatus including a spacer, since the spacer is provided in plural units according to the display area of the display panel or a thickness of the substrate for the rear plate and the face plate, the number of the spacers increases as the display area becomes larger or as the substrate becomes thinner. As a result, there increases a number of steps for positioning the spacers and there may result an increase in the manufacturing cost.
Also an operation of fixing the plural spacers or the plural support members to the face plate or the rear plate with the connecting members requires a longer time with an increase in the number of spacers, and there may also result an increase in the manufacturing cost.
Also in order to obtain a uniform image quality in the image display apparatus, there is required a high precision in the order of a micron in the fixing position of the spacer. However, a heating step for hardening a connecting member such as an adhesive to be used in fixing the spacer may cause a distortion by a thermal expansion in a jig for spacer fixation, thereby deteriorating the positional precision of the spacer fixation.
Also in forming an air-tight container by heat sealing the rear plate bearing the spacer and the face plate, or in driving the image display apparatus, there may result a dimensional difference by thermal expansion between the spacer and the face plate or rear plate bearing such spacer, thereby causing a destruction of the spacer.